Permanent magnet motor flux rings

ABSTRACT

A power tool includes a motor with a flux ring. The flux ring includes a ring member with a first and second end. The ends are positioned with respect to one another such that the ends move towards and away from one another during compressing and expanding of the ring. At least one anchor is unitarily formed with the ring. A pair of magnets are coupled with unitarily formed anchors to couple the pair of magnets with the ring. The magnets are coupled with the ring such that the ring may be compressed and expanded with the magnets secured in the ring.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to power tools and, more particularly, tomotors for the power tools which include flux rings.

In electric motor construction, the motor magnets must be retained onthe housing or on a separate flux ring positioned within the housing.Ordinarily, these magnets have been glued or adhered to the metallicflux ring or housing. When using a flux ring, different methods havebeen utilized to position the flux ring and magnets in the housing. Onesuch way is to position the flux ring within the housing and then addthe magnets onto the flux ring. Another method is to generally adherethe magnets onto a flux ring and then slide the flux ring into thehousing. Thus, it would be desirable to provide a flux ring with themagnets positioned on the flux ring which could be positioned into amotor housing and frictionally engage the motor housing to hold the fluxring in place during assembly.

The present invention provides the art with a flux ring which is capableof radial expansion and contraction with the magnets secured to the fluxring. In order to manufacture a motor with a flux ring, it is desirableto position the flux ring into the housing wherein the flux ringfrictionally engages the interior periphery of the housing until theflux ring is secured to the housing. Also, the flux ring minimizes thegap between its ends to provide maximum magnetic flux carrying capacity.

In accordance with a first aspect of the invention, a flux ringcomprises a ring member having a first and a second end. The ends arepositioned with respect to one another such that the ends move towardsand away from one another during compressing and expanding of the ringduring assembly. At least one anchor is unitarily formed with the ring.At least one magnet is coupled with the unitarily formed anchor tocouple the at least one magnet with the ring. The magnet is coupled withthe ring such that the flux ring may be compressed and expanded with theat least one magnet coupled with the ring during assembly. One of thefirst or second ends overlaps or meshes with the other end. The at leastone magnet is formed on the ring such that the magnet embeds with theanchor to couple the magnet to the ring. The first and second ends mayinclude at least one mating or meshing projection and receiving recess.The at least one magnet is injection molded onto the ring. The anchormay be an aperture in the ring with a counter-sink. Also, the anchor maybe a go member unitarily formed with the ring and radially projectingfrom the ring. A combination of the anchors may be used.

In accordance with a second aspect of the invention, an electric motorcomprises a motor can housing with a pair of end caps coupled to themotor can. A flux ring is positioned within the motor can housing. Theflux ring includes a ring member having a first and a second end. Theends are positioned with respect to one another such that the ends movetowards and away from one another during compressing and expanding ofthe ring during assembly. At least one anchor is unitarily formed withthe ring. At least one magnet is coupled with the unitarily formedanchor to couple the at least one magnet with the ring. The magnet iscoupled with the ring such that the flux ring may be compressed andexpanded with the at least one magnet coupled with the ring duringassembly. One of the first or second ends overlaps the other end. The atleast one magnet is formed on the ring such that the magnet embeds withthe anchor to couple the magnet to the ring. The first and second endsmay include at least one mating or meshing projection and receivingrecess. The at least one magnet is injection molded onto the ring. Also,the anchor may be an aperture in the ring with a counter-sink. Also, theanchor may be a member unitarily formed with the ring and radiallyprojecting from the ring. Also, a combination of the anchors may beused. An armature assembly is positioned in the motor can housing.

In accordance with a third aspect of the invention, a power toolcomprises a housing with a motor in the housing. The motor comprises amotor can housing with a pair of end caps secured to the motor can. Aflux ring is positioned within the motor can housing. The flux ringincludes a ring member having a first and a second end. The ends arepositioned with respect to one another such that the ends move towardsand away from one another during compressing and expanding of the ringduring assembly. At least one anchor is unitarily formed with the ring.At least one magnet is coupled with the unitarily formed anchor tocouple the at least one magnet with the ring. The magnet is coupled withthe ring such that the flux ring may be compressed and expanded with theat least one magnet coupled with the ring during assembly. One of thefirst or second ends overlaps the other end. The at least one magnet isformed on the ring such that the magnet embeds with the anchor to couplethe magnet to the ring. The first and second ends may include at leastone mating or meshing projection and receiving recess. The at least onemagnet is injection molded onto the ring. The anchor may be an aperturein the ring with a counter-sink. The anchor may be a member unitarilyformed with the ring and radially projecting from the ring. Also, acombination of the anchors may be used. An armature assembly ispositioned in the motor can housing. A power source is coupled with thehousing. An activation member is coupled with the motor and the powersource for energizing and de-energizing the motor. An output is coupledwith the motor such that the motor drives the output during energizingof the motor.

In accordance with a fourth aspect of the invention, a method ofmanufacturing electrical motors comprises the steps of forming a motorcan housing. A flux ring is formed having two ends such that the endsmove towards and away from one another during compressing and expandingof the ring during assembly. A pair of magnets are coupled withunitarily formed anchors on the flux ring. The flux ring is compressed,if necessary, with the magnets on the flux ring such that the flux ringhas an external diameter smaller than an internal diameter of the motorcan housing. The flux ring is inserted into the motor can housing. Theflux ring is expanded to frictionally engage the motor can housing. Theexpanding of the flux ring occurs in response to the release of thecompression force on the flux ring. The flux ring is secured to themotor can housing preferably by welding, clinching, fasteners or glue. Afirst motor cap assembly is secured to the motor can housing. A motorarmature assembly is inserted into the flux ring in the motor canhousing. A second end cap is coupled with the armature assembly and themotor can housing. The magnets are injection molded onto the flux ring.The flux ring is formed such that the first and second ends overlap oneanother in the expanded condition in the motor can housing. A portion ofthe overlapped ends are welded to the housing to secure the flux ring inthe motor can housing.

In accordance with a fifth aspect of the invention, a method ofmanufacturing a power tool comprises the steps of forming a motor canhousing. A flux ring is formed having two ends such that the ends movetowards and away from one another during compressing and expanding ofthe ring during assembly. A pair of magnets are coupled with unitarilyformed anchors on the flux ring. The flux ring is compressed, ifnecessary, with the magnets on the flux ring such that the flux ring hasan external diameter smaller than an internal diameter of the motor canhousing. The flux ring is inserted into the motor can housing. The fluxring is expanded to frictionally engage the motor can housing. Theexpanding of the flux ring occurs in response to the release of thecompression force on the flux ring. The flux ring is secured to themotor can housing preferably by welding, clinching, gluing, mechanicalfastening or the like. A first motor cap assembly is secured to themotor can housing. A motor armature assembly is inserted into the fluxring in the motor can housing. A second end cap is coupled with thearmature assembly and the motor can housing. The magnets are injectionmolded onto the flux ring. The flux ring is formed such that the firstand second ends overlap or mesh with one another in the expandedcondition in the motor can housing. A portion of the overlapped ormeshed ends are secured to the housing to fix the flux ring in the motorcan housing. A housing half is provided. The motor is positioned in thehousing half. An output is positioned in the housing half and coupledwith the motor. An activation member is positioned in the housing halfand electrically coupled with the motor and the power source to energizeand de-energize the motor which in turn drives the output. A secondhousing half is coupled with the first housing half to form the powertool. A power source is coupled with the housing and electricallycoupled with the motor.

Additional objects and advantages of the invention will become apparentfrom the detailed description of the preferred embodiment, and theappended claims and accompanying drawings, or may be learned by practiceof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of a power tool in accordance with thepresent invention.

FIG. 2 is a perspective view of a flux ring in accordance with thepresent invention.

FIG. 3 is an exploded view of a motor including a flux ring inaccordance with the present invention.

FIGS. 4, 4 a- 4 c illustrate assembly steps of a motor in accordancewith the present invention.

FIGS. 5a-5 d illustrate assembly steps of a power tool in accordancewith the present invention.

FIG. 6 illustrates another embodiment of a flux ring in accordance withthe present invention.

FIG. 7 illustrates an additional embodiment of a flux ring in accordancewith the present invention.

FIG. 8 illustrates an additional embodiment of a flux ring in accordancewith the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning to the figures, FIG. 1 illustrates a power tool, particularly adrill, which is designated with the reference numeral 10. The power tool10 includes a housing 12 which includes two halves which are integrallyconnected to one another. A motor 14 is positioned within the housing12. The motor 14 is coupled with an output 16 which includes a chuckingend 18. Also, the motor 14 is electrically coupled with an activationmember 20 as well as a power source 22, in this case a battery. Theactivation member 20 energizes and de-energizes the motor 14 which, inturn, ultimately rotates the chuck 18.

The motor 14 includes a stator assembly 30 which includes a motor canhousing 32, flux ring 34, and magnets 36 and 38. An armature 40 includesa shaft 42, a rotor 44 with laminations 46 and windings 48, and acommutator 50. The armature 40 is coupled with the shaft 42 andpositioned inside of the motor can housing 32. The motor also includesend plates 52 and 54. End plate 52 includes a bearing 56 which balancesone end of the shaft 42. The shaft 42 is coupled with a pinion 60 whichis part of the power tool output. Brushes 62 and 64 are associated withthe commutator 50. A bearing 70 is also coupled with the end plate 54 tobalance rotation of the shaft 42.

Turning to FIG. 2, the flux ring 34 is illustrated with magnets 36 and38. The magnets 36 and 38 are of a molded magnetic material. Preferably,the molded material is an injection molded material. The ring 34 isstamped and rolled and positioned within a die and the magnetic materialis molded onto the flux ring. Also, the ring could be a machined part.Further, the magnets could be preformed and glued in place on the ring.

The flux ring 34 includes anchors 80 to retain the magnets 36 and 38onto the ring 34. The anchors 80 may be of two types. First, anchor 82is an aperture formed in the flux ring 34. The aperture has a firstportion 84 and a second counter-sink portion 86. The counter-sinkportion 86 extends to the exterior 88 of the ring 34. As the moldedmagnetic material is received in the anchor 82, the molded materialembeds with the ring and has a neck 92 and a head 94. The neck 92 andhead 94 provide an overall rivet appearance. Thus, the head 94 acts toretain the magnets 36 and 38 on the ring 34. The ring 34 may becomprised of just a plurality of aperture anchors 82 to retain themagnets on the ring 34.

Additional anchors 96 may be utilized on the ring. Anchors 96 are shownradially projecting from the interior surface 98 of the ring 34.However, the anchors 96 could project radially outwardly from the ring34. Ordinarily, the anchors 96 are stamped or the like into the ring 34forming an aperture 100 immediately adjacent the projecting anchor 96.Thus, when the molded magnetic material forms around the projectinganchor 96, it likewise goes under the anchor to fill-in the aperture 100to embed the molded magnetic material with the anchor 96. This providesfor a firm securement of the magnet onto the ring 34.

The ring 34 includes a pair of ends 102 and 104. The ends 102 and 104overlap one another. The overlapping enables a substantially continuousmagnetic flux around the ring 34. Also, the ends 102 and 104 enableoverlap when the ring is compressed or expanded during positioning ofthe ring 34 into the motor can housing 32. Note that the ring 34 may becompressed and expanded with the magnets 34 and 36 already secured tothe ring. Also, the ends 102 and 104 provide a surface on the ring 34 tobe welded to the motor can 32.

Turning to FIG. 4, a better understanding of the manufacturing of themotor 14 will be had. The motor can housing 32 is provided with two openends. However, a drawn motor can could be used with a unitary end on themotor can. The ring 34 with the magnets 36 and 38 already on the ring 34is compressed, if necessary, such that the ring 34 has an outer diameterless than the inner diameter of the motor can housing 32. The ring 34,in a radially compressed condition, is placed inside of the motor can32. The compressive force is removed from the ring 34 enabling it toexpand. As the ring 34 expands, it frictionally engages the motorhousing 32 maintaining it in position on the housing 32. Also, the ringcould have an outer diameter less than the inner diameter of the motorcan. Thus, the ring would be forcibly expanded to frictionally engagethe motor can. The ring 34 is then secured to the motor can housing 32by welding, clinching (e.g. extruding the motor can housing into theflux ring or vice versa), gluing, mechanical fastening (e.g. rivets) orthe like. The ring is welded at ends 102, 104 to secure it with themotor can housing 32. Also, the ring 34 may be welded to the motor canat a position 180° from the ends. After welding, the end plate 52 ispositioned on one end of the motor can housing 32. The armature 40 withthe end plate 54 which includes the brushes 62 and 64 as well as thebearing 70 is inserted into the motor can housing 32. The end plate 54is coupled with the motor can housing 32 forming the motor 14.

Turning to FIG. 5, the above described motor 14 is positioned into ahousing half. The power tool output 16 with the chucking end 18 iscoupled with the motor 14. In turn, the activation member 20 ispositioned into the housing half and electrically coupled with the motor14. The second housing half is coupled with the first housing half.Thereafter, the power source 22, in this case a battery, is insertedinto the housing 12 and electrically coupled with the activation member20 which, in turn, is electrically coupled with the motor 14. Also, themotor, output and chuck, and activation member may be assembled togetherso that it is positioned as a unit into a housing half. The otherhousing half would then be coupled with the first housing half and thebattery would be added. When the activation member energizes the motor14, the output 16 rotates the chuck 18.

FIGS. 6-8 illustrate different ring embodiments. The difference betweenthe rings is at their ends.

FIG. 5 illustrates a ring 34′ which has ends 102′ and 104′. The end 104′includes a cut-out portion 206 with a projecting member 208. Theprojecting member 208 serves as a weld location. While a singleprojecting member 208 is shown, multiple members could be used.

FIG. 7 illustrates an additional embodiment of the present invention.Here, the ends 102″ and 104″ have alternating projections 304, 306 andrecesses 308, 310. The fingers and recesses enable meshing of the ends102″ and 104″. Gaps 312 and 314 are formed between the ends 102″ and104″. As the ring 34″ expands into the motor housing 32, the gap 312increases in size, while the gap 314 remains substantially constant insize. The gap 314 is maintained sufficiently small such that a weldeasily bridges between ends 102″ and 104″ to the motor housing 32.

FIG. 8 illustrates an additional embodiment of the ring 34′″. Here, end102′″ includes a pair of recesses 402 while end 104′″ includes a pair ofprojecting members 404. The projecting members 404 project into therecesses 402 and provide a weld location to weld the ring 341′″ to themotor can 32. Also, each end could include one projection and onerecess. Gaps 406 and 408 are formed between the ends 102′″ and 104′41 .As the ring 34′″ expands into the motor housing 32, the gap 406increases in size, while the gap 408 remains substantially constant insize. The gap 408 is maintained sufficiently small such that a weldeasily bridges between ends 102″′ and 104′″ to the motor housing 22.

Applicants would like to incorporate by reference the specification anddrawings of U.S. patent application Ser. No. 09/492,059 filed Jan. 27,2000 and entitled “ANCHORING SYSTEM FOR INJECTION MOLDED MAGNETS ON AFLUX RING OR MOTOR HOUSING”. The embodiments of the flux ringillustrated in the Ser. No. 09/492,059 application may be equallysubstituted in the present invention with the exception that the ends ofthe rings would be modified as described above with respect to FIGS. 2or 6-8.

While the above detailed description describes the preferred embodimentof the present invention, the invention is susceptible to modification,variation, and alteration without deviating from the scope and fairmeaning of the subjoined claims.

What is claimed is:
 1. A flux ring comprising: a ring member having afirst end and a second end, said ends positioned with respect to oneanother such that said ends move towards and away from one anotherduring compressing and expanding of said ring, respectively; at leastone anchor unitarily formed from said ring; at least one magnet embedswith said unitarily formed anchor for coupling said at least one magnetwith said ring, said magnet being coupled with said ring such that saidring may be compressed and expanded with said at least one magnetcoupled with said ring.
 2. The flux ring according to claim 1, whereinone of said first or second ends overlaps the other.
 3. The flux ringaccording to claim 1, wherein said first and second ends include atleast one mating or meshing projection and recess.
 4. The flux ringaccording to claim 1, wherein said at least one magnet being injectionmolded onto said ring.
 5. The flux ring according to claim 1, whereinsaid anchor being an aperture in said ring, said aperture including acounter-sink portion.
 6. The flux ring according to claim 1, whereinsaid anchor being a member unitarily formed with said ring and radiallyprojecting from said ring.
 7. An electric motor comprising: a motor canhousing; two end caps each coupled to said motor can housing; a fluxring secured with said motor can housing, said flux ring including: aring member having a first end and a second end, said ends positionedwith respect to one another such that said ends move towards and awayfrom one another during compressing and expanding of said ring duringassembly; at least one anchor unitarily formed from said ring; at leastone magnet embeds with said unitarily formed anchor for coupling said atleast one magnet with said ring, said magnet being coupled with saidring such that said ring may be compressed and expanded, duringassembly, with said at least one magnet coupled with said ring; and anarmature assembly positioned in said motor can housing.
 8. The electricmotor according to claim 7, wherein one of said first or second endsoverlaps the other.
 9. The electric motor according to claim 7, whereinsaid first and second ends include at least one mating or meshingprojection and recess.
 10. The flux ring according to claim 7, whereinsaid at least one magnet being injection molded onto said ring.
 11. Theelectric motor according to claim 7, wherein said anchor being anaperture in said ring, said aperture including a counter-sink portion.12. The electric motor according to claim 7, wherein said anchor being amember unitarily formed with said ring and radially projecting from saidring.
 13. A power tool comprising: a housing; a motor in said housing,said motor comprising: a motor can housing; two end caps each coupled tosaid motor can housing; a flux ring secured with said motor can housing,said flux ring including: a ring member having a first end and a secondend, said ends positioned with respect to one another such that saidends move towards and away from one another during compressing andexpanding of said ring during assembly; at least one anchor unitarilyformed from said ring; at least one magnet embeds with said unitarilyformed anchor for coupling said at least one magnet with said ring, saidmagnet being coupled with said ring such that said ring may becompressed and expanded, during assembly, with said at least one magnetcoupled with said ring; an armature assembly positioned in said motorcan housing; a power source; an activation member coupled with saidmotor and said power source for energizing and de-energizing said motor;and an output coupled with said motor such that said motor drives saidoutput during energizing of said motor.
 14. The power tool according toclaim 13, wherein one of said first or second ends overlaps the other.15. The power tool according to claim 13, wherein said first and secondends include at least one mating or meshing projection and recess. 16.The flux ring according to claim 13, wherein said at least one magnetbeing injection molded onto said ring.
 17. The power tool according toclaim 13, wherein said anchor being an aperture in said ring, saidaperture including a counter-sink portion.
 18. The power tool accordingto claim 13, wherein said anchor being a member unitarily formed withsaid ring and radially projecting from said ring.